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4.3 notes


John Scott

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Guest Anonymous

I am excited about the possibility of doing this unconventional swap over the 383. I say possibility because if I can't sell my 383 components than I can't do the 4.3. How much does the 4 bolt conversion cost?

 

SpencZ

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The price of two 4 bolt splayed caps plus re-machining the block to accept them.(Chevy has billit splayed, also Milodon others.) Drilling, tapping, align bored/ honed. I'd call a good machine shop for a quote. By the time you build up a motor from the start + the supercharger/ turbo, + the intercooler., distrib, intake, etc.. Its all going to be pretty pricey. (I think sanderson makes block huggers. I had mine hand built.) Probably more than the 383 build up. If you want the extra room and like the idea of the 'chargedV6, then jump in! I've never had so much fun with an engine! How many ponies do you want to get from your engine???

John

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Before anyone runs out and buys an engine a few bits of info. might be needed. The 4.3 which is really a 3/4 350 smallblock (cyls 3 and 6 are missing) was first built in 1985. This is the only year for the 2 piece crankshaft seal. 86 and up will all be 1 piece. An adapter is made by chevy to swap the two designs. In 1987 the blocks went to roller camshaft designs. otherwise remained the same. Somewhere down the 4.3 line they added a balance shaft to the engine. This is not the model you want. The 4.3 engine has the familiar 4 inch bore and 3.48 stroke of the 350. Rod length is also identical, but the 4.3 has a unique big end bearing size and width. This is a true even fire block with crank pin offsets to give the 120 degrees between firings. An odd fire,not to be confused with the semi evenfire earlier small displacement blocks, is offered by some aftermarket companies for max. effort v6s. This allows the use of the v8 style rods. The Syclone guys running 10 sec.1/4s will tell you the stock crank is fine with the four bolt conversion. They also recommend the later 93-96 heads and rods from 96-98. I haven't verified this so you may want to do some of your own research. Chevy says the stock rods are great if they are prepared as in the Chevy power catalog/manual. I suggest buying this book if you start building the 4.3. Valve train, pistons, bearings, mains, oilpumps, water pumps, etc can all be shared with the small block. With few modifications they claim the 4.3 can live above 7500 rpm, but I think the ticket to power is what the Typhoon/Syclone racers are doing: Large boost #s at under 6000 rpm. I think anyone building this engine will be happy with the durability and performance!

John Scott

 

[This message has been edited by John Scott (edited April 16, 2000).]

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Guest Anonymous

I have had a second thought about all this...why the he!! would I go and sell all of my 383 stroker parts and get rid of my block to go and spend more money on another engine??? I must have been temporarily drunk because this just doesn't make any sence! I am back to the 383 stroker but still plan on dreaming of my blown 4.3L AWD Z car!!

 

SpencZ

MonsterZ Cont. http://members.xoom.com/SpencZ/index.htm

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Guest Anonymous

Being a Syclone owner and having spent some years on the SyTy mailing list I have some comments:

 

Stock motors come with hypereutectic pistons so plan accordingly. The short block for the SyTy wasn't changed all that much from the production ones. Materials change in the bearings was the biggest. There's an SAE paper on the 4.3 motor and another detailing the differences between the 4.3 and SyTy short block, FWIW.

 

For more SyTy info go to www.syty.org

As an added bonus someone came up with a chip editor for the 749 ECM. Check the diy_efi pages and look for promgrammer.

 

The biggest drawback, IMO, about the stock SyTy EFI setup is that it only has a 2 bar MAP sensor. Anything more than 14psi of boost is read as 14psi of boost by the computer. Small but important detail when considering fueling! Note there is a group of guys that have come up with a 3bar setup. Their price is ~$300 with multiple settings. Unfortunately, I've misplaced the URL.

 

Hope this is useful!

Scott

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Thanks for the info Scott. The hypereutectic pistons, (high silicon content) though much better than the stock pistons, are still not up for a lot of abuse. Forged is really the only way to go with a blown motor.

Have you done anything to the engine on your Syclone? Tell me about the content in the Ty/Sy bearings.( I went to a "H".)

John Scott

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Guest Anonymous

Re- hyperute pistons: They're ok as long as you don't detonate, but forged gives more margin for error! smile.gif Most of the SyTy guys that hurt motors bend rods from detonation. 5 head bolts per cylinder makes for a good seal!

 

Re--My Syclone is still stock. I have two other project cars taking up all my time and money. I have plans, but a lack of funding puts a serious crimp in the wrench budget! frown.gif

 

Re--SAE paper: I'll get the #s and give a brief summary tonight, when I'm at home.

 

Honestly, though, if you're going to go boost happy I think the 3.8L is the way to go. Better understood, more tuning tools (are't chip editors free?), and more R&D behind it. The 4.3L is nice from a displacement standpoint, though!

 

Scott

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Scott, I'm in love with the 4.3! Everything chevy makes for the small block will fit in there. Very successful racing history as well. No chips on my motor. Just trial and error. No detonation tonight at 16 psi!(no where near red line, On pump gas!) Pretty wild ride, can't keep up with boost gauge, tach, and trying to keep it straight!

John Scott

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Guest Anonymous

Synopsis of differences between SyTy 4.3 short block and standard production 4.3,

according to SAE paper #910682:

 

8.35:1 CR (vs 9:1) via new pistons

 

Main bearing cap material was changed to nodular iron from grey iron

 

minimum safety factor on the crank was reduced 33%

 

Redline is 4800 rpm to avoid extreme loading on rod

 

Different headgasket

 

Essentially, they tested with an engine putting out double the power of the production stuff and tweaked from there.

 

Re-- As for being busy driving to watch all the gauges, I have two words for you: Data Acquisition! :-)

 

Scott

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  • 3 weeks later...

Ok Scott, after much research, I've decided to go with chevy 4.3 with a ATI blow thru like yours! If you can provide me with what you've done and the parts you've used, I would be greatful! My ride is a 72 Z and I'm currently in the process of upgrading the rearend with a R200 with 3.36 gears! I want to go 5 or 6 speed haven't decided yet and upgrading the suspension with urethane bushing, progressive rate springs, struts and sway bars. I've ordered the JTR manual for tips( I need to strenghten the chassis ) and want to upgrade to brakes all around. Thanks for all the helpful info!

 

------------------

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Welcome to the world of 3/4 smallblocks! I have tons of info. on the 4.3 supercharged from piston #s to cam profiles for different boost #s. This could get real lengthy, I will forward the information to your Email. If you can, go out and buy the chevy power catalog, from a Chevy dealer, the one that details the chevy engines, and their buildups. This way you'll have all the machining clearences, recommendations etc. In addition to part#s, I'll also give you carb #s, jetting tips, timing curves, fuel pressures, everything to get you off to a good start. You'll still have plenty of big headaches, but hopefully you won't have to make as many mistakes as I did. (If anyone else wants all the nitty gritty on the internals,I'll be glad to send/or post it here.)

John

 

 

 

[This message has been edited by John Scott (edited May 10, 2000).]

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  • 2 months later...
Guest Anonymous

John Scott- do you have a website? You seem to know a hella-lot on this subject. You should compile/publish a book like JTR.

 

Also, Since the engine is basically a 350 with 3&6 missing and the engine mounts (jtr) would mount it 4-5 inches in front of the firewall (in a "scarab" posistion) the engine should fit nicely in a 280zx? right? Everyone says the firewall is 3 inches forward compared to the 240/60/80z ..? What do you think?

 

::crossing fingers::

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Paradox, Thanks for inflating my ego!! My wife would surely boot me out if I had any involvement in the Z beyond this site. Someday, I'll get around to putting up at least a webpage.

I'm not familiar with the engine bay of the ZX. My hours, days, perhaps the best years of my life biggrin.gif have been spent solely in the bay of a 72! If you use the JTR mounts on the 4.3, then yes it will put the engine one cylinder forward of the firewall as compared to the sbc. If the ZX firewall is 3 inches forward, then it should be a pretty easy, fit. SBC is 21.78" 4.3 is 17.38. Difference of about 4 1/2 inches. If 1 1/2" is crucial to your sense of vehicle balance, with a little tweaking of the JTR mounts, you could probably push it somewhat closer to the firewall. If not, then you'd probably cuss a lot less than the rest of us when you go to work on those &%$!! bellhousing bolts.

JS

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Guest Anonymous

Totally sweet. Now I just need to find a 4.3 engine. Which do you think is a better option, turbo or supercharger? I've heard turbos are better for smaller/lightweight cars because you have traction, then the psi hits, as opposed to superchargers used for big heavy metal monsters. Is this true?

 

I'm speculating the 4.3 swap (425 lbs. aiming for 300hp), or a 2.3 ford turbo (380 lbs aiming for 250+ hp).. I've got the body/frame, but $$ is tight.( I'm a college student on a budget) I'm not sure which would be cheaper, right now it looks like the ford.

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First of all Turbo/Supercharging a 4.3 is not going to be cheap. Forged pistons, custom ground cam, conversion to 4 bolt mains,(highly recommended from my twisty main caps) rod work, etc, etc, Perhaps a complete Syclone motor, intercooler, with computer would be the ticket for a turbo set up.

Unless you're planning on running a roots style blower, low end will be similar with a supercharger (centrifugal) to a turbo. These have little or no boost off the line then increase with rpm. Great for the light limited traction Z. I can launch mine w/o much more than a squeak from the tires. At a 25 mph punch, its a different tire melting story. The Turbo will be more complicated, but probably yeild more hp throughout the rpm range. I don't what you'd be facing with the Ford turbo. Do they make a rear wheel drive platform? If so then its just a matter of fabricating some mounts, cross member, driveshaft, shifter and some of the usual wiring headaches. On a budget? The 4.3 with it's roots to the sbc would make a good non supercharged motor as well. This is a sizible displacement motor with 262 cubic inches. Save on the price of supercharging and go with a healthy cam, good manifold, and even the stock 9.3:1 pistons can yeild pretty good perf. I had a great 150K mi time on my '74 Hilux P/U with the same 4.3 I'm running now. Only a custom ground comp cam and 700r4. I wish I could post the pictures (on video) of its funny car burnouts. Really torquey with its 3.06 1st and 4.11s! Let me know if I can help.

JS

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  • 10 years later...

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